Method and apparatus for liquefaction of neon

ABSTRACT

1,186,432. Turbines. NAUTCHNO-IZSLEDOVATELSKI SEKTOR PRI PHISITCHESKIA FAKULTET NA SOFIISKI UNIVERSITET. April 3, 1967 [April 1, 1966], No. 6881/67. Heading F1T. [Also in Division F4] A turbo-expander suitable for cooling neon gas for providing refrigeration comprises a turbine rotor 70 mounted on a vertical shaft 62 having radial gas bearings 65 and a lower end thrust gas bearing 68 supplied with compressed neon at 54, 55 and having exhaust outlets 66, 67; the shaft also carrying an energy absorbing fan 69 supplied with neon through an inlet 52 and the compressed neon discharged at 53 is cooled in a nitrogen bath before being returned to the fan inlet.

Oct. 21, 1969 E. 1. LEYAROVSKI ETAL 3,473,342

METHOD AND APPARATUS FOR LIQUEFACTION OF NEON 4 Sheets-$heet 1 FiledApril 5, 1967 E G A R o T S COMPRESSOR NITROGEN BATH COMPRESSOR 32 TURBONEON 'GAS STORAGE TURBO EXPANDER NlTROGEN BATH lllfillllll ll.

L 10 asp/0 60L E'IVOID CO/LS Oct. 21, 1969 E. l. LEYAROVSKI ETAL3,473,342

METHOD AND APPARATUS FOR LIQUEFACTION OF NEON Filed April 5, 1967 4Sheets-Sheet 2 E (J 51 a wi wa 52 H,-1 HH1-45 -WM m W Ml'i "m M- M M,glg 55 OOOOOO-g 58- fi J 60 Get. 21, 1969 E. LEYAROVSKI ETAL 3,473,342

METHOD AND APPARATUS FOR LIQUEFACTION OF NEON Filed April 5, 1967 4Sheets-Sheet 5 FIG. 2A

Oct. 21, 1969 E. 1. LEYAROVSKI ETAL 3,473,342

METHOD AND APPARATUS FOR LIQUEFACTION OF NEON 4 Sheets-Sheet -1 FiledApril 5, 1967 United States Patent int. (311F255 1/02 US. Cl. 62-9 5Claims ABSTRACT OF THE DISCLOSURE Method of compressing large volumes ofneon for liquefaction of large volumes for industrial use andpreliminarily cooling the compressed neon and expanding a portion of thecooled compressed neon in a throttling process expansion and a serieswork expansion thereby further cooling it. The expanded neon is used tocool the remainder of compressed neon which is subsequently throttled orexpanded to liquify it.

Apparatus compressing neon and cooling it comprising means to divide thecompressed neon main flow and expand a part thereof in a turboexpanderand using the expanded cooled neon to cool compressed unexpanded neon,in a heat exchanger group, which is then throttled and liquefied by amain throttle. The neon itself thus provides the principal coolingagent.

The present invention relates to a method and apparains for liquefying agas and more particularly for liquefaction of neon.

There are two principal known methods for liquefying gas neon. A firstmethod is a cycle based on simply throttling the gas after preliminarycooling with liquid nitrogen. The final etiiciency of this cycle isquite low. In order to obtain an acceptable coefiicient of liquefaction(0.15- 0.18) it is necessary to subject the neon to a very highcompression pressure, for example 100 to 220 atmospheres, which resultsin the consumption of a very large amount of energy and the need ofheavy and expensive apparatus. A second known method for liquefaction ofneon is based on condensation of neon conveyed through a bath of liquidhydrogen. The method is very simple and effective but the system forliquefying the neon depends on a system for liquefying hydrogen which isvery expensive and dangerous. The liquefaction of one liter of neon inthis system requires the evaporation of about four liters of hydrogen.Thus this second method is practical for production of large quantitiesor volumes of liquid neon only in the vicinity of very large sources ofliquid hydrogen.

It is a principal object of the present invention to provide a new andimproved, simple and inexpensive apparatus and method of liquefaction ofneon with a minimum expenditure of energy input.

According to the method of the invention the shortcomings of thedescribed methods are overcome. The method makes use of an isentropicexpansion of a part of the neon flow after preliminary cooling thereofwith liquid nitrogen and the expanded cooled neon cools the unexpandedneon which is then liquefied by throttling. This method allows reductionof the compression pressure applied to neon to about 30 atmospheres. Theenergy consumption, proportional to the ratio of the pressure, isdiminished about six times in comparison with the method described, witha cycle of simple throttling. The reduction in work input is veryimportant in industrial production of liquid neon. Moreover, the methodaccording to the ice invention eliminates the use of liquid hydrogenwhich is both very expensive and dangerous to handle.

A feature of the method for liquefaction of neon according to theinvention makes use of a combined cycle consisting of preliminarycooling, by means of nitrogen throttling and expansion of a part of thecompressed neon in a turboexpander and using the expanded neon forcooling compressed neon which is throttled after cooling to liquefy it.The main source of cooling is the neon itself since the expanded neon isdirected in a counter-flow heat exchanger arrangement to cool unexpandedcompressed neon of the main flow.

The use of a turboexpander for liquefaction of neon is quiteadvantageous and particularly more advantageous than using hydrogen orhelium as a cooling agent since the velocity of the sound is small whichmakes it possible to realize the cycle with isentropic expansion of thegas without the shortcomings inherent in other expansion apparatus, forexample an expansion apparatus.

Other features and advantages of the method and apparatus in accordancewith the present invention will be better understood as described in thefollowing specification and appended claims in conjunction wtih thefollowing drawings in which:

FIG. 1 is a schematic diagram of apparatus according to the inventionand a flow chart of a cycle of the method according to the invention;

FIG. 2 is a diagrammatic vertical section view of apparatus for neonliquefaction provided with the invention;

FIG. 2A is a diagrammatic enlarged vertical view of a part of theapparatus in FIG. 2; and

FIG. 3 is a fragmentary longitudinal section view of a turboexpander ofFIG. 2 on an enlarged scale.

The method and cycle of the apparatus for carrying out the invention andthe principles thereof are illustrated in FIG. 1. In accordance with theinvention neon gas is stored in a storage tank or container 1 from whicha compressor 2 takes a suction and compresses the neon to a highpressure, in the order of 30 atmospheres. The gas is then dischargedthrough a line 3 to a heat exchanger 4 where it is cooled by reverseflow neon under low pressure to about 78 degrees K. The high pressureneon is illustrated by solid lines, a continuation of line 3, andreverse flow cooling neon, obtained as later explained is illustrated bya broken line 5. The main flow of neon is subjected to cooling in a heatexchanger 6 immersed in a nitrogen bath 7, vented by a vapor vent 9, andcontinues to be cooled in a heat exchanger 11 cooled by the reverseflowneon. After having passed through the heat exchanger illustrateddiagrammatically the main stream or fiow of compressed neon is dividedand a portion thereof is taken through a flow path 13 to a throttlevalve 14 where it is throttled or expanded to some intermediate pressurebetween that pressure at which it is received at the throttle and apressure when it leaves a turboexpander 16 where the throttled neon isexpanded to about one atmosphere. The expansion of the neon at thethrottle valve 14 and the turboexpander 16 is an expansion Withoutchange of entropy.

The expansion of the neon is without exchange of heat and results in atemperature drop. The cooled, expanded neon is applied downstream of aheat exchanger 17 so that it reverse fiows back to the source 1 throughthe various heat exchangers mentioned heretofore cooling the main flowof compressed neon. A heat exchanger 20 receives that main flow ofunexpanded, high-pressure neon and a back flow of neon vapors as laterexplained cools it. The neon vapors cooling the heat exchanger 20 jointhe expanded, cooled reverse-flow neon intermediate the heat exchangers17 and 20. Cooling of the high pres- 6 sure neon is now at an optimumlevel for the extent of throttling that is to take place forliquefaction of the neon.

The main fiow of compressed neon is throttled by a main throttle 22where a part of it is liquefied. The liquid obtained, mixed withsaturated vapors, is applied to cooling the coils 23 of a large solenoidimmersed in a neon bath 24 in a container or receptacle 25. The mixtureof liquefied neon and saturated neon vapors obtained after the throttlevalve 22 passes through the coils of the powerful solenoid 23 and takeaway its heat, and the saturated neon vapors from the receiver 26 arerecycled as they cool off the heat exchanger 29 and receive the neonvapours discharge from the turboexpander and are passed, through heatexchangers 17, 11 and 4 in sequence and being delivered of their cold,are gathered in the source or receiver 1 from which the compressor 2takes a suction again so that a regenerative cycle as described above isrealized.

The entire cycle is maintained in a vacuum insulation and when necessaryliquefied neon can be drawn out of the liquefier in Dewar vacuum vessels(not shown).

The turboexpander 16 has connected thereto a turbocompressor 32 whichtakes a suction on a neon gas storage or neon source 33 through a flowpath or line 34 and compresses the neon and discharges it through adischarge path 36 to a heat exchanger 37 immersed in a nitrogen bath 39where the neon is cooled and it is then returned to the source 33. Thusthe energy delivered by the expansion of the neon is dissipated or takenout in the form of heat in the nitrogen bath 39.

The drawing illustrates in FIG. 2 diagrammatically apparatus forcarrying out liquefaction as heretofore described with respect to thediagram and flow chart in FIG. 1. The apparatus comprises a liquefiercomprising a vessel 45 covered with a cover 46 from which is suspended,for example by welding, coaxially with the vessel an inner conduitsupport 47, made for example of stainless steel, defining a spacebetween it and the vessel 45. Within this space is disposed a Hempsonheat exchanger 49 comprising a leader distributor or collector 51 towhich is delivered compressed neon through an inlet pipe 53 receivingneon under pressure, for example about 30 atmospheres, from acompressor, not shown, as described with respect to the compressor 2 inthe diagrammatic illustration of the invention. The vessel 45 is aninsulated vessel and has a highly efficient heat insulation jacketconsisting of a jacket 52 evacuated and under a high vacuum, so that anyheat exchange is substantially impossible between apparatus within thevessel and the exterior thereof. The vacuum is taken by means not shown.

The compressed neon gas flows through the pipes of heat exchanger 49 andis cooled by the counter flow of low pressure neon in the intertubespace. The high pressure neon is discharged to a ring header 55 incommunication with a similar ring header or collector 55 disposedcircumferentially of the central support 47. The collector 56 isimmersed in a main nitrogen bath 58. The nitrogen extends downwardly asa nitrogen screen 50 in communication with the main bath 58. The mainbath is supplied with liquefied nitrogen through a line 54 and icontained in a conical space of the liquefier below the heat exchanger49 and boils at a pressure approximate to atmospheric pressure and coolsto 7778 K. The header 56 discharges into a coil 60 in communication withanother header 62 which supplied a Hempson heat exchanger 63 incommunication with a collector or outlet header 65 in communication withan inlet ring or header 68 delivering high pressure neon to a Hempsonheat exchanger 70 terminating in a collector or header 71 which deliversthe high pressure neon to a heat exchanger 7 3 at the lower part of thevessel.

All of the heat exchangers are cooled by neon in a back or reverse flowthrough intertube spaces thereof. The

coil 50, like the coil 6, is immersed in the nitrogen bath 58.The-topmost heat exchanger 49 is mounted above this bath and like theother heat exchangers is cooled by the 'low pressure neon which passesthrough the intertube spaces of the various heat exchangers and isdischarged through a return conduit 76 for return to the supply source 1as heretofore described. The heat exchanger 45 is insulated by the lowpressure neon vapors and wound around the central line 47 and is cooledby nitrogen vapors, from the nitrogen bath 58 which are discharged tothe atmosphere through a vent 75.

A compartment 81 wherein a turboexpander 9%, later herein described, ismounted, is connected to the body or the liquefier 52 by means of aflange 8t). The same is connected to the general vacuum of the liquefierby means or a flange 84 and a vacuum connection 82.

The turboexpander is supplied with high pressure neon by means of aconnection 89 which divides the main neon flow by a deviation of a linebetween collectors 65 and 68. This high pressure neon is throttledthrough a throttle valve 87 which corresponds to the throttle valve 14,to about ten (10) to fifteen (15) atmospheres gauge and it supplies theturboexpander 90 after which the neon, eX- panded to about two (2)atmospheres, is passed through a copper line 93 connected to the bottomof the heat exchanger 79 and incorporates the neon vapors to the generallow pressure neon flow of the liquefier.

It is understood that the connection in the low pressure neon flow isreadily directed upstream in the heat exchanger 75 as far as the coolingneon flow is concerned. A valve 88 performs the function of controllingthe neon gas fed to the gas containers of the turboexpander.

The high pressure neon which leaves thegroup of heat exchangers isdelivered through a line 95 into a line 99 which goes on into a coilmounted on the bottom of a neon container 193 wherein the cooling of thehigh pressure neon is completed and then the neon is throttled throughthe main throttle valve 98 corresponding to the throttle valve 22 ofFIG. 1. The throttled and expanded neon is delivered in a liquid statemixed with saturated vapors through a line 163 for cooling of the coilof a powerful solenoid 102 immersed in a neon bath 193 contained in acontainer 104 which is screened by a nitrogen screen 105 and which isconnected expressly for the purpose to a nitrogen bath M6 contained in acontainer 197 wherein liquid nitrogen is fed through a line 109. Thenitrogen vapors from the container 107 exit into the outer atmospherethrough a line 164. This entire arrangement in conjunction with thelower end of the vessel 45 is disposed internally of an insulatingcompartment or jacket 111i covered with a vacuum-tight cover 111 andheld under vacuum in conjunction with the expansion or throttle valve 93by the means supplying vacuum to the main vessel jacket and the othercompartment 81 supported on the liquefier vessel jacket or housing.

The low pressure neon vapors taken from the top part above the level ofthe liquid neon in the neon container 153 through a line 116 are passedinto the lower end or the central structure of the liquefier and as theypass and cool in sequence heat exchangers 73, 76, 63 they pass throughlines 165 into the bottom part of heat exchanger 49 and after they havecooled it they pass through line 76 into the receiver (1). From therethey are again taken as a suction by the compressor 2. The possibilityis provided to draw out liquid neon through the line which is immersedin the neon bath 193 in case this is necessary.

The turboexpander 90 is shown in detail in FIG. 3 and comprises a nozzle12% receiving neon gas under high pressure from the main stream asexplained heretofore delivered into a chamber 122, in communication withthe supply inlet line 89, defined jointly by a housing 123 and a nozzlethroat piece 124. The neon is then at about a pressure of from ten tofifteen atmospheres. The neon under pressure delivered by the nozzledrives a rotor 126 having a diffuser 127 for carrying out the expansionof the neon without exchange of heat thereby effecting a temperaturedrop therein as heretofore described. The diffuser 127 discharges to thedischarge line 93 With which the throat piece 124 is in communication.

A shaft 129 is driven by the rotor 126 driving an impeller 133 in aturbine casing 134 of a turbocompressor 135 taking a suction from a neonstorage or source 136, FIG. 2, compressing the neon and discharging itinto a heat exchanger 138 immersed in a nitrogen bath 140 supplied withnitrogen by a line 142. The energy delivered by the expanding neon inthe turboexpander 90 is removed as heat by the nitrogen bath 140.

The rotor shaft 129 is mounted in a vertical position to preclude anysag since it operates at high speeds, for example over 100,000revolutions per minute. The weight of the rotor assembly and the axialreaction forces applied thereto by the expanding neon stream are takenup by a thrust bearing 138. Cooled neon under pressure from the mainstream is delivered into a space in the bearing housing through acontrol passageway 140 connected to a neeon manifold 148. The neon isthrottled or expanded in the clearances between the bearing and itshousing and discharged through an outlet 145 connected to a dischargemanifold 144 in communication with the expanded low-pressure neon of thesystem.

The rotor is mounted on aerostatic bearings 150, 151, receiving highpressure neon through respective control inlets 153, 154. The neon issupplied to respective annular chambers 156, 157 and escapes along theclearance space between the shaft and the housing and is dischargedthrough an outlet 160 in communication with the outlet manifoldheretofore described.

The turboexpander assembly is effectively sealed with labyrinth seals161 at the end of the rotor and a labyrinth 162 about the rotatingdiffuser 127.

Thus those skilled in the art will understand that the inventionprovides a highly simplified and compact apparatus and a highlyeffective and inexpensive method and cycle and mode of operation of theapparatus for inexpensive production of large volumes of industrialliquid neon.

While preferred embodiments of the invention have been shown anddescribed it will be understood that many modifications and changes canbe made within the true spirit and scope of the invention.

What we claim and desire to be secured by Letters Patent is:

1. A method of liquefying large volumes of neon comprising, providingneon in a gaseous state to be liquefied, compressing the neon to beliquefied, expanding a portion of the cooled, compressed neon to coolit, cooling the remainder of the compressed neon with said expanded andcooled neon, and expanding and cooling the remainder of the cooledcompressed neon to liquefy at least a part of said remainder of neon andexpanding a portion of said cooled, compressed neon comprisingthrottling said portion of neon and thereafter work expanding the neonimmediately before cooling the remainder of the compressed neon withsaid expanded and cooled neon.

2. Apparatus for liquefying large volumes of neon gas comprising, asource of compressed neon under high pressure, means to cool thecompressed neon under high pressure, means to remove a-portion of thecooled compressed neon including first means to expand it in a throttleprocess expansion and a work expansion serially without exchange of heatin at least one of the expansions thereby further cooling the expandedneon, other cooling means additionally cooling said neon under highpressure, means to apply the cooled, expanded neon to said other coolingmeans to cool said neon under high pressure, and second means to expandthe additionally cooled, unexpanded neon under high pressure thereby toliquefy it.

3. Apparatus according to claim 2, in which said first means to expandthe high pressure neon comprises a first throttle effecting an expansionto a lower pressure and a turboexpander in series with said firstthrottle.

4. Apparatus according to claim 2, in which said first means to expandthe high pressure neon comprises turboexpansion means expanding the neonsubstantially with out exchange of heat thereby cooling the neonexpanded.

5. Apparatus according to claim 2, in which said first means to expandthe high pressure neon comprises a throttle and a turboexpander inseries, and said second means to expand high pressure neon comprises amain throttle.

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